If it is given arguments, there can be any number of them (actually, no more than 255, but this won't stop most people), but they must all be numbers 1 to 3. Then, the command will only turn on the specified plots. Unlike some commands, it is okay to give PlotsOn an expression as an argument (for example, PlotsOn X), as long as it has a value of 1, 2, or 3.